I have a 13cu and it provides quite a bit of room, you should be happy with 15.7. Have you searched the DIY
There are some great projects. Most just go with a simple collar for keezers but it sounds like you might want to take some of the kegerator conversion threads to heart if you want to go with a tower. I personally wouldn't want to do anything but a simple collar as I'm going to keep the freezer dual purpose (serving and fermentation on and off).
The troubles of our proud and angry dust
Are from eternity, and shall not fail.
Bear them we can, and if we can we must.
Shoulder the sky, my lad, and drink your ale.
A. E. Housman
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